Multiple switchboard for telephone-exchanges.



PATENTED SEPT. 26, 1905 I 'M. G. QKBLLOGG. MULTIPLE SWITGHBOARD. FOR TELEPHONE EXCHANGES APPLIG'ATIQNTILBD Nov. 30, 1891.

UNITED STATES PATENT OFFICE.

MILO G. KELLOGG, OF CHICAGO, ILLINOIS, ASSIGNOR TO KELLOGG SWITCHBOARD AND SUPPLY COMPANY,

CORPORATION ILLINOIS.

OF CHICAGO, ILLINOIS, A

MULTIPLE SWITCHBOARD FOR TELEPHONE-EXCHANGES.

Specification of Letters Patent.

Patented Sept. 26, 1905.

Application filed November 30, 1891. Serial No. 413,606.

To all whom it mag concern:

- with a switch-plug which may be inserted;

and it consists of a system of calling, switchlng, testlng, and clearing-out connections,

which I shall describe and claim in detail.

-In the drawings illustrating my invention, Figure 1 represents front views of sections of two switchboards with metallic sockets or switch-terminals for several lines and two lines connected to the two boards with their line-annunciators, retardation-coils, and central-oflice connections. Fig. 2 shows an operators cord system adapted to be used at each board; Fig. 3, an operators test system adapted to be used at each board, and Fig. '4: a diagram of the subscribers-station apparatus for each line. Fig. 5 indicates a polarized calling-annunciator for the lines.

In Fig. 1, A A are the two switchboards. j j are metallic sockets or switch-terminals, one for each line on each board. Each socket or switch-terminal is adapted to receive and form connection with each switch-plug at its board. (Shown in Fig. 2 and marked D D.) to w are the line-annunciators, and w a" retarda tion-coils, one annunciator and one retardation-coil for each line. Each line is connected to its metallic socket or switch-terminals on the boards and is grounded through its annunciator and retardation-coil, as shown. It is preferable, as will hereinafter appear, that the annunciators be polarized annunciators and be connected in the circuits, as will hereinafter be indicated. The retardation-coils are not necessary, but are desirable to retard the passage to ground at the central office of telephone-currents which may be passing over the circuit of two lines connected together for conversation. The annunciators' may be so constructed as to offer the retardationeflect required.

The polarized line-annunciator is shown in Fig. 5, N S indicating the poles thereof, 0 the armature, and P the shutter or drop.

In Fig. 2, D D are a pair of switch-plugs, each adapted to be inserted into the switch-terminals and form the connections, as heretofore described. 70 70 are two calling-keys, one for each plug. Each key has a lever connected by a flexible conductor with its plug and a contact-point normally in contact with the lever and another contact-point normally out of contact with the lever. depressed, it passes out of contact with the first contact and into contact with the secondmentioned contact. tact is connected with the similar contact of the other key. Y is a switch, 0) a clearing- The first-mentioned con- When the lever is out annunciator, and X a retardation-coil for the pair of plugs. tis the operators telephone. B is acalling-generator, and B atestbattery, of which there may be one of each for the exchange. The lever of the switch Y is connected with the two contacts of the key which are normally in contact with the key-levers. The other contacts of the keys are connected to ground through the callinggenerator. One of the switch-bolts on which the levermay be placed by the operator is connected through the clearing-out annunciator and retardation-coil of the pair of plugs and the test-battery to the ground, Other pairs of plugs with their special apparatus may be connected to the operators cord system substantially as shown and as will be evident to those skilled in the art.

- In the operators test system shown in Fig. 3, T is the test-plug, which is adapted to be brought into connection for testing with any metallic socket or switch-terminal j at its apparatus shown in Fig 4, 1 is the telephoneswitch. 2 is the signal-receiving bell. 3 is the calling-generater. 4 is the operators telephone, and 5 is a calling-key. The generator is constructed with the usual automatic device whereby it is shunted or switched from theline-circuitwhile not operated. The insulated contact-piece on the shaft of the armature, to which is connected one end of the armature-wire and which conducts the generated current to the line through the stationary spring-contact (or contacts) provided for it, is a halt-circle, the remaining part of the circle being an insulation. as shown. Iprovide two stationary spring conconnection of the key to the contact-springs of the generator and to the line-circuit is as follows and as shown: The spring-lever,

which forms one of the contacts of each pair of contact-points, is connected with one side of the main-line circuit. The two other contact-pieces of the pairs of contact-points are connected to the two contact-springs, respectively. As stated above, one end of the armature-wire is connected with the halfcircle contact-piece on the generator-shaft, on which the springs alternately bear when the generator is being turned. The other end of the armature-wire is connected with the other side of the main-line circuit.

The automatic shunt device mentioned before may shunt that part of thecircuit containing the armature-wire and the key when the generator is not being operated upon.

It is well known that when magneto-generators are turned and operated a current of one polarity is generated during one half of the revolution of the armature and a current of the other polarity is generated during the other half of the revolution of the armature.

It will be apparent from the description of the subscribefis-station apparatus which has been given and from the circuits that when the generator is being operated and the key remains in its normal position the armature- Wire is in circuit through one of the contactsprings. and that only, and a current of one polarity will be sent to the line, and that when the generator is being operated and the key is depressed the armature-wire is in circuit through the other contact-spring, and that only, and a current of the other polarity will be sent to the line. The subscriber can therefore at will send currents of either polarity to line as he does not or does press on the calling-key.

The line-annunciators should preferably be connected into their respective circuits in such a direction as to be operated by the current from the subscribers generator when it is operated while the calling-key is not depressed.

The clearing-outannunciators may be nonpolarized annunciators.

The test-battery should preferably be con nected in such a direction that when it is connected to the circuit of any line by means of a switch-plug being inserted into the terminal of the line its current will be ol the same polarity or direction in the line as is the current from the line-generator when it is operated and the subscribers key is depressed.

The operation of the system is as follows: hen a subscriber desires to make a call, he operates his generator without pressing his key 5. A calling-current; is thereby sent to the line which operates the lineannuneiator. The operator then places one ot the switieh plugs into the switch-terminal ot' the line and places the switch Y, so that her telephone is in circuit with the line and [bids out by conversation what line is wanted. She then tests the line wanted, as will be described, and if she tinds that it is free or unswitehed she places the other plug ol the pair in its switch-tern'iinal at her board. The two-lines are then connected in a circuit. and the circuit is grounded at the central otiire through the annunciator and retardationcoil of each line. The operator then presses the key whose lever is connected with the plug which is colllieeted with the calling-line and by so doing disconnects the line from the other and grounds it through the calling-generaton and a callingcurrent goes to the line, which rings the subscribers bell. The operator then moves the lever of the switch Y, so that the circuit is grounded through the anmmciatior and retardation coil ot' the pair of plugs used. The lines are thus connected together l'or conyersation, and the circuit is grounded through the annunciator and retarilat'ion-coils of both lines and of the pair of plugs. The retardation effect of the almunciators and ret'ardation-coils will, however, be such as not to interl'ere with the telephone-currents which may pass over the circuit.

The operators callirig-generator B should preferably be such as to give but one polarity of current and should be so connected as not in calling to send the polarity oi current to the lines which will operate their annuneiators, and the subscribefis signal receiving bell should be such as to respond to currents of that character. Any usual forms of apparatus which produce these results may be used.

The test system is as follows: \Vhen a line is switched for conversation, its circuit is grounded through the test-battery B. It when it is in that condition a testplug is applied to its switch-terminal at any board, a complete test circuit is established which contains the battery and the operators test-receiving instrument, and the instrument will sound, in-

' through the -test-plug and test-receiving instrument to the ground. When aline is tested which is not switched for use, no circuit is established which contains the operators test-receiving instrument and a battery, and

' the instrument will not sound, and the operbusy.

- through it.

ator thereby knows. that the line is not switched. When the calling-generator B is connected to aline-circuit and the line is tested, there will be a current from the generator through the I test receiving instrument which will give an indication that the line is or a clearing-out annunciator is connected to the line, the test indication comes from the battery B. In any case, therefore, the line will test busy when a switch-plug is in one of its metal sockets or terminals.

The battery B should not be strong enough to operate any clearing-out annunciator when connected to the circuit of two lines, as described. It will, however, reinforce the. clearlng-out current sent from either station and may be of such strength as to do this in amaterial way. With certain forms of apparatus this may be necessary or desirable, as only part of the current generated when a clear-. 'ing -out slgnal 1s glven goes through the clearing-out annunciators, the remainder going to ground through the line-annunciators of the two lines and the subscribers ground of the line in which the clearing-outsignal did not originate.

As shown in the drawings and described herein, a retardation-coil or its equivalent is preferably used in circuit with the clearingout annunciator. This circuit is therefore of comparatively high resistance, and a correspondingly small amount of the clearing-out current sent by the subscriber will pass The use of the battery B to reinforce the current and secure the operation of the annunciator is therefore desirable.

Instead of the annunciator w and retardation-coil as for each line an annunciator may be employed which has high resistance and high retardation to telephone-currents.

I claim as my invention 1 1. In a telephone-exchange system, a pair of switch-plugs and two calling-keys, one for each plug, each having a lever connected with the plug by a flexible switch-conductor, a contact-point normally in contact with the lever and in electrical connection with the corresponding point of the other key and a contact-poiut-normally out of contact with the lever, each lever being adapted tobe pressed away from the point with which it is normally 1n contact and into contact with the other point of the key, in combination with-a When either the operators telephone calling-generator grounded on one side and connected on the other side to each of sardcontact-points normally out of contact with its lever, a battery grounded on one side, a clearing-outannunciator connected on one side to'the other side of said battery and a switch with contacts to connect said annunciator on its other side to the circuit connecting said first-mentioned contact-points, substantially, as set forth.

2. In a telephone-exchange system, a pair of switch-plugs and two calling-keys, one for, each plug, each having a lever connected with the plug by a flexible switch-conductor, a contactpoint normally in contact'with the lever and in electrical connection with the corresponding point of the other key and a contact-point normally out of contact with the lever, each lever being adapted to be pressed away from the point with which it isnormally in contact and into contact with the other point of the key, in combination w1th a calling-generator grounded on one side and connected on the other side to eachof said contact-points normally out of contact with its lever, a battery grounded on one side, aclearing-out annunciator and retardation-coil in a circuit connection connected on one side to the other side of said battery, and a switch with contacts to connect said circuit connection on its other side to the circuit connecting said first-mentioned contact-points, substantially as set forth.

3. In a telephone-exchange system, a pair of switch-plugs and two calling-keys, one for each plug, each having a lever connected with the plug by aflexible switch-conductor, acontact-point normally in contact with the lever and in electrical connection with the corresponding point of the other key, and a contact-point normally but of contact with the lever, each lever being adapted to be pressed away from the point with which it is normallyin contact and into contact with the other point of the key, in combination with a calling-generator grounded on one side and connected on the other side to each of said contact-points. normally out of contact with its lever, a battery grounded on one side, a clearing-out annunciator and an operators telephone each connected on one side to the other side of said battery, and a switch with contacts to connect either said annunciator or said telephone on its other side to the circuit connecting said first-men tionedcontact-points, substantially as set forth.

4. In a telephone-exchange system, a pair of switch-plugs and two calling-keys, one for each plug, each having a lever connected with I the plug by a flexible switch-conductor, a contact-point normally in contact with the lever and inelectrical connection with the correspondin g point of the other key and a contactpoint normally out of contact with the lever, each lever being adapted to be pressed away &

from the point with which it is normally in contact and into contact with the other point of the key, in combination with a calling-generator grounded on one side and connected on the other side to each of said contact-points normally out of contact with its lever, a battery grounded on one side, an operators telephone, a clearing-out annunciator and a retardation-coil in acircuit connection, said telephone and said circuit connection being each connected on one side to the other side of said battery, and aswitch with contacts to connect at will said telephone and saidcircuit connection on their other sides to the circuit connecting said first-mentioned contact-points, substantially as set forth.

5. In a telephone-exchange system,two lines connected together for conversation and their circuit grounded through the polarized annunciator of each line, in combination with a clearing-out annunciator and a battery on a circuit connection from the circuit of said lines to the ground, said battery being so connected as not to cause the magnets of said polarized annunciators to attract their armatures in the direction to operate the annunciators and being so related to said clearing-out annunciator as to cause the magnet to attract its arn'iature but not suflicientl y to operate the annnnciator and means whereby either subscriber may send over the line a current of a polarity that will not operate the line-amiunciators but will operate the clearing-out annunciator, substan tially as set forth.

6. In a telepholie-exchange system, two lines grounded at their outer ends and connected together for conversation, in combination with a clearing-out annunciator and a battery in a circuit connection from the circuit of said lines to the ground, said battery being so related to said clearing-out annunciator as to cause the magnet to attract the armature but not sufficiently to operate the annunciator, and means whereby either subscri ber may send over the line a current which reinforces the battery-circuit to operate the an nnncia tor su bstantially as set forth.

In testimony whereof I have hereunto subscribed my name.

MILO G. KICLLOG (i.

WVitn esses:

ANNA KELLOGG, LEROY L). KuLLooo. 

